For those whom get tired of collecting all kinds of weapons just so you can do extra damage to certain types of enemies. I present to you the All Slayer Set for 5e. The creator of these items is myself, the referenced characters Beazilbe, i have gained permission from that player to use his characters name.
Mind you i didn't really have a chance to play test them beyond basic self encounters, and they were designed mostly for the fighters whom late game don't really have as many damage dealing options as some of the other classes, other than to stock up on various weapons like the giant slayer, or Frost Brand. So the All-Slayer set was made to mediate this weapon bog down.

The All Slayer is a weapon that when you hit a target they must make a consave (increases based on weapon rarity) on a failed save that target then will take an extra 3d6 weapon damage. The all slayers also have an added elemental damage with the use of a command word. Finally The All Slayer are very heavy, because of the weight you must have a minimum amount of strength to use them, lest you want to have disadv on the attack rolls.

Minor all slayer weapons are +1, deal an extra 2d6 weapon damage on failed save, and an extra 1d6 elemental damage. They are of Rare quality. Requiring a 14 strength for two handed style, and 16 strength for one handed. DC 15 con save
Moderate All Slayer Weapons are +2, also deal 2d6 extra weapon damage on failed save, and 1d8 elemental damage. They are of Very-Rare quality. Requiring a 16 strength for two handed style, and 18 strength for one handed. DC 17 con save
Major All Slayer Weapons are +3, dealing 3d6 extra weapon damage on failed save, and 1d10 elemental damage. They are of Legendary quality. Requiring a 18 strength for two handed style, and 20 strength for one handed. DC 23 con save
True All Slayer Weapons are +5, dealing 3d6 extra weapon damage on failed save, and 1d12 elemental damage. They are of Artifact quality. Requiring a 20 strength for two handed style, and 22 strength for one handed. DC 27 con save